John thomson



J. THOMSONI METHOD FOR PREVENTIYG ELECTRIC CARBON RESISTERS FROMOXIDIZING.

APPLiCATlON FILED OCT.7, 1918.

1,308,878. Patented July 8, 1919.

Z INVENTOR BY UNITED STATES PATENT OFFICE.

' 101m THOMSON, or new roux, N. i.

Application flled October 7, 1918. Serial No. 257,213.

To all whom it may concern:

ing.

Be it known that I, JOHN THOMSON, a citizen of the United States, and aresident of the borough of Manhattan, city of New York, county and Stateof New York, have invented certain new and useful Improvements inMethods for Preventing Electric CarbonResisters from Oxidizing, of whichthe following is a specification.

This invention relates to electric furnaces and consists in a method forpr'eventin carbon 'resisters from oxidizing, or airurn- The accompanyingdrawing is a-diagrammatic sectional view of an electric furnacecomprising the essential elements necessary to illustrate the presentmethod. In said dra-Win in whic A is the base, B the side-walls, and

C the arched roof that together provide the furnace chamber D. Mountedin the sidewalls, and passing through the chamber, is a carbon resisterE whose type is commonly designated as the zig-zag, its terminals beingempirically shown in a power-circuit F,

Hitherto, the chief difficulty, and to a large extent the limitingfactor, in the use of electric carbon resisters, irrespective of theirtype or form, is their liabilit to attack and disintegration when air orot er active gases are present in the resistor-chamber. A method hashitherto been employed to avoid the destruction of carbon resisters, asby the introduction of an inert gas. For an example of such method seeU. S. patent to F. A. J. FitzGerald, No. 950,905, dated March 1, 1910.Said method has proven fairly successful; but the method now to bedescribed is more generally applicable in present practice and possessescertain impontant advantages.

Thus, the method now to be described consists of locating within aresister-chamber a charge composed of a mixture of oxid of zinc (ZnO)and carbon '(C), which, when sufiiciently heated, reacts according tothe classical. formula,

If or when any oxygen is present in the resister-chamber, it combineswith the zincfume and produces ZnO, whereby the resister itself is madewholly immune to pernicious attack; or, as expressed in commonparlance,-is immune to air-burning.

Specification of Letters Patent.

a furnace construction is shown- Patented Ju y s, 1919.

The mixed charge, as h, may be convenlently introduced to theresister-chamber,

from time-to-time, through an opening or. tube, as m, to be received bya pan, as n resting upon the resistor, or it may be dropped upon thebottom of the chamber, as at 1-. The tube may also be utilized as avent, as at s,wherea t to burn a flame of mixed or intermingled Znfumeand CO, thereby indieating to an operator thatthe chamber contains anadequate supply of thebenign vapor and gas.

It is preferable, for the present purpose,"

that both the zinc oxid ZnO and the carbon C which compose the chargeshall be of a high degree of purity, whereby the residuum of thereaction shall be a merely nominal amount; and also in that there shallbe practically no other development of vapor and gas than pure zinc-fumeand monoxid of carbon. v

Obviously, the charge needs not be located precisely within the confinesof the resistorchamber; for, if desirable, it might be placed in acommunicating side-chamber, or niche, or wherever sufficient heat couldbe directed thereon to produce the reaction; which becomes active at orabout 1,000 C.

The following controlling advantages reside in the production ofzinc-fume by'means of the aforesaid reaction rather than by merelyvaporizing metallic zinc: Firstly, the CO performs the function of anactive carrier for the denser Zn vapor or fume and serves to convey 'thelatter into any crevices in the furnace-walls'whereat, if air ispresent, it will burn to ZnO, thus automatically closing the vents andexcluding a further entrance of oxygen. Secondly, the expansion of thefume and gas, particularly when the resister chamber is wholly inclosed,produces pressure, of which but a nominal amount is necessary to causethe reaction. to cease. Consequently, when there are no vents to permitescape of the fume and gas, or when no oxygen is present to consume thefume, the reduction of the charge is automatically suspended; and, percontra, if vents develop, and if air again enters, the benign reactionis automatically resumed. In these circumstances, a merely nominalquantity of reacting charge serves to protect-the resister for arelatively long period of time. In fact, carbon resisters have been thuscontinuously operated, at high temperatures, for periods of months,without the slightest deterioration; the conditions of service beingsuch that, without the utilization of this' method, they would not haveendured but a few hours. 4 p

While the foregoing matter has preferably dealt specifically with themetallic vapor produced from oxid of zinc and the gas resulting from itsreagent, monoxid of carbon, the method, broadly, is not necessarilyconfined to these specific substances,; in that the oxid of any metal,when combined with any suitable reagent whose reaction will produce ametallic vapor which combines with oxygen, and a gas which will'notattack carbon, may. be utilized. c

What I claim is:

1. In electric furnaces, the method of preventing a carbon resistor fromoxidizing which consists in locating a charge of oxid of zinc and carbon(ZnO and 0) within the resistor-chamber and heating the said chargeuntil it reacts and produces zinc fumes and carbon monoxid (Zn and CO.)v

2. In electric furnaces, the method of preventing a carbon resister fromdestructive G0), which method consists in so situatin a charge of oxidof zinc and carbon (Zn and 0) within a resistor-chamber, that theingredients of the charge will be caused to react until the developedpressure is sufiicient to automatically sus nd the reaction.

4. In electric furnaces, t e method of preventing a carbon resistor fromoxidizing which method consists of envelopin the resister in anatmosphere comp of the fumes or vapors from a vaporized metallic oxidand its gaseous reducing reagent.

This specification signed and witnessed this 13th day of September, A.D. 1918.

, JOHN THOMSON.

Signed in the presence of RALPH M. THOMSON, H. O. Wain).

